FIGS. 3 and 4 show structural examples of a test head used for a semiconductor test system in a conventional technology. In the conventional test head technology for a semiconductor test system, a plurality of printed circuit boards (pin electronics card or pin card) are mounted on a back board for securing a mechanical strength with respect to the test head 6. As shown in the front view of FIG. 3 and in the side view of FIG. 4, a plurality of pin cards 4 are mounted on the back board 1 at the bottom of the test head 6. At the top of the pin cards 4, a mother board 2 is connected to the pin cards 4 through connectors 3. As is known in the art, each of the pin cards 4 includes an electronic component such as a driver, a comparator and switches to provide a test signal to a terminal pin of a device under test. The number of the pin cards 4 corresponds to the maximum number of the terminal pins of a device to be tested.
In general, a semiconductor device to be tested is mounted on a performance board 7. The mother board 2 functions as an interface for electric connection between the performance board 7 and the pin cards 4. Namely, the mother board 2 establishes electronic paths to provide the test signals from the pin cards 4 to the device under test through the performance board 7 as well as the resultant response signals from the device under test to the pin cards 4. The back board 1, in contrast, functions to mechanically support the pin cards 4 in the test head 6 in the accurate positions when the connectors of the pin cards are inserted in the sockets on the back board 1.
In the conventional technology, in order to replace the pin card 4 in the test head 6, the mother board 2 has to be removed from the test head by disconnecting from the connectors 3 which are connected to the pin cards 4.
Recently, the size of the mother board 2 is significantly increased with the increase of functionality of the semiconductor test system. Hence, the mother board 2 can be as large as one square meter and as heavy as 20 kg. When trouble occurs in the pin card 4 or when the pin card is to be replaced because of a model change, for example, the mother board 2 and the pin card 4 must be disconnected to exchange the pin card 4. Because of the size and weight of the mother board as noted above, an operator had to bear a significant burden for such replacement, and thus the efficiency of the replacement is significantly low. Further, the number of pins in each connector 3 to connect between the pin card 4 and the back board 1 or the pin card 4 and the mother board 2 tends to increase with the increase of the scale of the semiconductor test system. Therefore, there is a drawback in the conventional technology that it is necessary to include an additional mechanism for maintaining contact reliability of the electric connection or a mechanism for promoting connection and disconnection of the mother board with less power.
As in the foregoing, in the test head structure of the conventional technology for mounting the pin cards on the boards in the test head, (1) the mother board has to be taken out every time when the pin card must be changed, (2) the work for taking out the mother board is a significant burden for a user due to the size and weight of the mother board, and (3) the additional mechanism for maintaining the contact reliability at the connection area or the mechanism for assisting the connection and disconnection of the mother board with less power is necessary.